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FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
NAME
ftnchek - Fortran program checker
SYNOPSIS
ftnchek [ -arguments=num ] [ -array=num ] [ -[no]backslash
]
[ -[no]calltree ] [ -columns=num ] [ -common=num ]
[ -[no]crossref ] [ -[no]declare ] [ -[no]division ]
[ -[no]extern ] [ -[no]f77 ] [ -[no]help ]
[ -[no]hollerith ] [ -include=str ] [ -[no]library ]
[ -[no]list ] [ -makedcls=num ] [ -[no]novice ]
[ -output=str ] [ -[no]portability ] [ -[no]pretty ]
[ -[no]project ] [ -[no]pure ] [ -[no]reference ]
[ -[no]resource ] [ -[no]sixchar ] [ -[no]sort ]
[ -[no]symtab ] [ -[no]tab ] [ -[no]truncation ]
[ -usage=num ] [ -[no]verbose ] [ -[no]volatile ]
[ -wordsize=num ] [ -wrap=num ] [ files ... ]
DESCRIPTION
ftnchek (short for Fortran checker) is designed to detect
certain errors in a Fortran program that a compiler usu-
ally does not. ftnchek is not primarily intended to
detect syntax errors. Its purpose is to assist the user
in finding semantic errors. Semantic errors are legal in
the Fortran language but are wasteful or may cause incor-
rect operation. For example, variables which are never
used may indicate some omission in the program; uninitial-
ized variables contain garbage which may cause incorrect
results to be calculated; and variables which are not
declared may not have the intended type. ftnchek is
intended to assist users in the debugging of their Fortran
program. It is not intended to catch all syntax errors.
This is the function of the compiler. Prior to using
ftnchek, the user should verify that the program compiles
correctly.
This document first summarizes how to invoke ftnchek.
That section should be read before beginning to use
ftnchek. Later sections describe ftnchek's options in
more detail, give an example of its use, and explain how
to interpret the output. The final sections mention the
limitations and known bugs in ftnchek.
INVOKING FTNCHEK
ftnchek is invoked through a command of the form:
$ ftnchek [-option -option ...] filename [filename ...]
2 June 1995 1
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
The brackets indicate something which is optional. The
brackets themselves are not actually typed. Here options
are command-line switches or settings, which control the
operation of the program and the amount of information
that will be printed out. If no option is specified, the
default action is to print error messages, warnings, and
informational messages, but not the program listing or
symbol tables.
Each option begins with the '-' character. (On VAX/VMS or
MS-DOS systems you may use either '/' or '-'.) The
options are described at greater length in the next sec-
tion.
ftnchek options fall into two categories: switches, which
are either true or false, and settings, which have a
numeric or string value. The name of a switch is prefixed
by 'no' to turn it off: e.g. -nopure would turn off the
warnings about impure functions. The 'no' prefix can also
be used with numeric settings, having the effect of turn-
ing off the corresponding warnings. Only the first 3
characters of an option name (not counting the '-') need
be provided. A colon may be used in place of an equals
sign for option value assignments; however, we show only
the equals sign form below.
The switches and settings which ftnchek currently recog-
nizes are:
-arguments=num
Set level of strictness in checking subprogram
arguments. Min is 0 (no checking). Max is 3 (most
checking). Default = 3.
-array=num
Set level of strictness in checking array arguments
of subprograms. Min is 0 (least strict). Max is 3
(most strict). Default = 3.
-backslash
Handle UNIX-style backslash escapes in character
strings. Default = no.
-calltree
Print tree of subprogram call hierarchy. Default =
no.
-columns=num
Set maximum line length to num columns. (Beyond
this is ignored.) Max is 132. Default = 72.
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FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
-common=num
Set level of strictness in checking COMMON blocks.
Min is 0 (no checking). Max is 3 (must be identi-
cal). Default = 3.
-crossref
Print cross-reference list of subprogram calls and
COMMON block use. Default = no.
-declare
Print a list of all identifiers whose datatype is
not explicitly declared. Default = no.
-division
Warn wherever division is done (except division by
a constant). Default = no.
-extern
Warn if external subprograms which are invoked are
never defined. Default = yes.
-f77 Warn about extensions to the Fortran 77 Standard.
Default = no.
-help Print command summary. Default = no.
-hollerith
Warn about Hollerith constants if -portability
option is in effect. Default = yes.
-include=path
Define a directory to search for INCLUDE files.
Cumulative.
-library
Begin library mode: do not warn about subprograms
in file that are defined but never used. Default =
no.
-list Print source listing of program. Default = no.
-makedcls=num
Prepare a file of declarations. Min is 0 (no dec-
laration file). Max is 511. Default = 1 if this
option is specified with an out-of-range numeric
value.
-novice
Give output suitable for novice users. Default =
yes.
-output=filename
Send output to the given file. Default is to send
output to the screen. (Default filename extension
2 June 1995 3
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
is .lis).
-portability
Warn about non-portable usages. Default = no.
-pretty
Give warnings for possibly misleading appearance of
source code. Default = yes.
-project
Create project file (see explanation below).
Default = no.
-pure Assume functions are pure, i.e. have no side
effects. Default = yes.
-reference
Print table of subprograms referenced by each sub-
program. Default = no.
-resource
Print amount of resources used in analyzing the
program. Default = no.
-sixchar
List any variable names which clash at 6 characters
length. Default = no.
-sort Print list of subprograms sorted in prerequisite
order. Default = no.
-symtab
Print symbol table for each subprogram. Default =
no.
-tab Accept DEC-style tab-formatted source. Default =
no.
-truncation
Check for possible loss of accuracy by truncation.
Default = yes.
-usage=num
Control warnings about unused variables, etc. Min
is 0 (no checking). Max is 3 (most checking).
Default = 3.
-verbose
Produce full amount of output. Default = yes.
-volatile
Assume COMMON blocks lose definition between acti-
vations. Default = no.
2 June 1995 4
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
-wordsize=num
Set the default word size for numeric quantities to
num bytes. Default = 4 bytes.
-wrap=num
Set output column at which to wrap long error mes-
sages and warnings to the next line. If set to 0,
turn off wrapping. Default = 79.
When more than one option is used, they should be sepa-
rated by a blank space, except on systems such as VMS
where options begin with slash ( / ). No blank spaces may
be placed around the equals sign ( = ) in a setting.
ftnchek "?" will produce a command summary listing all
options and settings.
When giving a name of an input file, the extension is
optional. If no extension is given, ftnchek will first
look for a project file with extension .prj, and will use
that if it exists. If not, then ftnchek will look for a
Fortran source file with the extension .for for VMS sys-
tems, .f for UNIX systems. More than one file name can be
given to ftnchek, and it will process the modules in all
files as if they were in a single file.
Wildcards are allowed in the specification of filenames on
the command line for the VMS and MS-DOS versions, as also
of course under UNIX and any other system that performs
wildcard expansion in the command processor.
If no filename is given, ftnchek will read input from the
standard input.
OPTIONS
This section provides a more detailed discussion of
ftnchek command-line options. Options and filenames may
be interspersed on a command line. Most options are posi-
tional: each option remains in effect from the point it is
encountered until it is overridden by a later change.
Thus for example, the listing may be suppressed for some
files and not for others. Exceptions are: the -wordsize
setting, which cannot be changed once processing of input
files has started; the -arguments, -array, -calltree,
-common, -crossref, -extern, -reference, -resource, -sort,
and -volatile options, where the action depends only on
the value of the option after the processing of input
files is finished; and the -include setting, which is
cumulative.
The option names in the following list are in alphabetical
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FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
order.
-arguments=num
Controls warnings about mismatches between actual
and dummy subprogram arguments. (An actual argu-
ment is an argument passed to the subprogram by the
caller; a dummy argument is an argument received by
the subprogram.)
The meanings of the setting values are as follows:
0: turn off all such warnings.
1: warn only about different number of arguments.
2: warn only about mismatch of data type of argu-
ments and of function itself.
3: all warnings.
Default = 3.
This setting is provided mainly to suppress warn-
ings when you wish to use ftnchek for some other
purpose than checking for errors, for example when
you only want to print the call tree. It does not
apply to checking invocations of intrinsic func-
tions or statement functions.
See also: -array, -library, -usage.
-array=num
Controls the degree of strictness in checking
agreement between actual and dummy subprogram argu-
ments that are arrays. The warnings controlled by
this setting are for constructions that might
legitimately be used by a knowledgeable programmer,
but that often indicate programming errors.
The meanings of the setting values are as follows:
0: only warn about cases that are seldom inten-
tional (see note below).
1: warn if the arguments differ in their number of
dimensions, or if the actual argument is an
array element while the dummy argument is a
whole array.
2: warn if both arguments are arrays, but they
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FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
differ in number of elements.
3: give both types of warnings.
Default = 3.
Note: A warning is always given regardless of this
setting if the actual argument is an array while
the dummy argument is a scalar variable, or if the
actual argument is a scalar variable or expression
while the dummy argument is an array. No warning
is ever given if the actual argument is an array
element while the dummy argument is a scalar vari-
able. Variable-dimensioned arrays and arrays
dimensioned with 1 or asterisk match any number of
array elements. There is no check of whether
multi-dimensional arrays agree in the size of each
dimension separately.
See also: -arguments, -library, -usage.
-backslash
Handle UNIX-style backslash escapes in character
strings. The escape sequence following the back-
slash will be evaluated according to the ANSI stan-
dard for strings in C: up to three digits signify
an octal value, an x signifies the start of a hex-
adecimal constant, any of the letters a b f n r t
signify special control codes, and any other char-
acter (including newline) signifies the character
itself. When this option is in effect, a non-
standard warning will be given if the -f77 flag is
set. Default = no.
If this option is turned off (the default), the
backslash will be treated like any other normal
character, but a warning about portability will be
generated if the -portability flag is set. Because
of the fact that some compilers treat the backslash
in a nonstandard way, it is possible for standard-
conforming programs to be non-portable if they use
the backslash character in strings.
Since ftnchek does not do much with the interpreted
string, it is seldom necessary to use this option.
It is needed in order to avoid spurious warnings
only if (a) the program being checked uses back-
slash to embed an apostrophe or quote mark in a
string instead of using the standard mechanism of
doubling the delimiter; (b) the backslash is used
to escape the end-of-line in order to continue a
string across multiple source lines; or (c) a
2 June 1995 7
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
PARAMETER definition uses an intrinsic string func-
tion such as LEN with such a string as argument,
and that value is later used to define array dimen-
sions, etc.
-calltree
Causes ftnchek to print out the call structure of
the complete program in the form of a tree. The
tree is printed out starting from the main program,
which is listed on the first line at the left mar-
gin. Then on the following lines, each routine
called by the main program is listed, indented a
few spaces, followed by the subtree starting at
that routine. Default = no.
If a routine is called by more than one other rou-
tine, its call subtree is printed only the first
time it is encountered. Later calls give only the
routine name and the notice ``(see above)''.
Note that the call tree will be incomplete if any
of the input files are project files containing
more than one module that were created in -library
mode. See the discussion of project files below.
Technical points: Each list of routines called by a
given routine is printed in alphabetical order. If
multiple main programs are found, the call tree of
each is printed separately. If no main program is
found, a report to that effect is printed out, and
the call trees of any top-level non-library rou-
tines are printed. This flag only controls the
printing of the call tree: ftnchek constructs the
call tree in any case because it is used to deter-
mine which library modules will be cross-checked.
See the discussion of the -library flag.
See also: -crossref, -library, -reference, -sort,
-symtab.
-columns=num
Set maximum statement length to num columns.
(Beyond this is ignored.) This setting is provided
to allow checking of programs which may violate the
Fortran standard limit of 72 columns for the length
of a statement. According to the standard, all
characters past column 72 are ignored. If this
setting is used when the -f77 option is in effect,
a warning will be given for any lines in which
characters past column 72 are processed. Max is
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FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
132. Default = 72.
-common=num
This setting varies the strictness of checking of
COMMON blocks.
The different levels are:
0: no checking.
1: in each declaration of a given COMMON block,
corresponding memory locations (words or bytes)
must agree in data type.
2: also warn if different declarations of the same
block are not equal in total length.
3: corresponding variables in each declaration of
a block must agree in data type and (if arrays)
in size and number of dimensions.
Default = 3.
The Fortran 77 Standard requires each named common
block, but not blank common, to be the same length
in all modules of the program. Level 3 provides an
extra degree of checking to support a frequent pro-
gramming practice.
See also: -library, -usage, -volatile.
-crossref
Specifies that a cross-reference table be printed.
This table lists each subprogram followed by a list
of the routines that call it. Also prints a table
listing each COMMON block followed by a list of the
routines that access it. Default = no.
The cross-reference listing omits library modules
that are not in the call tree of the main program.
The list is alphabetized. The routines listed as
using a COMMON block are those in which some vari-
ables in the block are accessed, not simply those
routines that declare the block. (To find out what
routines declare a COMMON block but do not use it,
see the -usage flag.)
See also: -calltree, -reference, -sort, -symtab.
2 June 1995 9
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
-declare
If this flag is set, all identifiers whose
datatype is not declared in each module will be
listed. This flag is useful for helping to find
misspelled variable names, etc. The same listing
will be given if the module contains an IMPLICIT
NONE statement. Default = no.
See also: -sixchar, -usage.
-division
This switch is provided to help users spot poten-
tial division by zero problems. If this switch is
selected, every division except by a constant will
be flagged. (It is assumed that the user is intel-
ligent enough not to divide by a constant which is
equal to zero!) Default = no.
See also: -portability, -truncation.
-extern
Causes ftnchek to report whether any subprograms
invoked by the program are never defined, or are
multiply defined. Ordinarily, if ftnchek is being
run on a complete program, each subprogram other
than the intrinsic functions should be defined once
and only once somewhere. Turn off this switch if
you just want to check a subset of files which form
part of a larger complete program, or to check all
at once a number of unrelated files which might
each contain an unnamed main program. Subprogram
arguments will still be checked for correctness.
Default = yes.
See also: -library.
-f77 Use this flag to catch language extensions which
violate the Fortran 77 Standard. Such extensions
may cause your program not to be portable. Exam-
ples include the use of underscores in variable
names; variable names longer than six characters;
statement lines longer than 72 characters; and non-
standard statements such as the DO ... ENDDO struc-
ture. ftnchek does not report on the use of lower-
case letters. Default = no.
See also: -portability, -pretty, -wordsize.
2 June 1995 10
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
-help Prints a list of all the command-line options with
a short description of each along with its default
value. This command is identical in function to
the ``?'' argument, and is provided as a conve-
nience for those systems in which the question mark
has special meaning to the command interpreter.
Default = no.
The help listing also prints the version number and
patch level of ftnchek and a copyright notice.
Note: the ``default'' values printed in square
brackets in the help listing are, strictly speak-
ing, not the built-in defaults but the current val-
ues after any environment options and any command-
line options preceding the -help option have been
processed.
-hollerith
Hollerith constants (other than within FORMAT
specifications) are a source of possible portabil-
ity problems, so when the -portability flag is set,
warnings about them will be produced. If your pro-
gram uses many Hollerith constants, these warnings
can obscure other more serious warnings. So you
can set this flag to ``no'' to suppress the warn-
ings about Holleriths. This flag has no effect
unless the -portability flag (which is off by
default) is turned on. Default = yes.
See also: -portability.
-include=path
Specifies a directory to be searched for files
specified by INCLUDE statements. Unlike other com-
mand-line options, this setting is cumulative; that
is, if it is given more than once on the command
line, all the directories so specified are placed
on a list that will be searched in the same order
as they are given. The order in which ftnchek
searches for a file to be included is: the current
directory; the directory specified by environment
variable FTNCHEK_INCLUDE if any; the directories
specified by any -include options; the directory
specified by environment variable INCLUDE; and
finally in a standard systemwide directory
(/usr/include for UNIX, SYS$LIBRARY for VMS, and
\include for MSDOS).
2 June 1995 11
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
-library
This switch is used when a number of subprograms
are contained in a file, but not all of them are
used by the application. Normally, ftnchek warns
you if any subprograms are defined but never used.
This switch will suppress these warnings. Default
= no.
This switch also controls which subprogram calls
and COMMON block declarations are checked. If a
file is read with the -library flag in effect, the
subprogram calls and COMMON declarations contained
in a routine in that file will be checked only if
that routine is in the main program's call tree.
On the other hand, if the -library switch is turned
off, then ftnchek checks the calls of every routine
by every other routine, regardless of whether those
routines could ever actually be invoked at run
time, and likewise all COMMON block declarations
are compared for agreement.
(If there is no main program anywhere in the set of
files that ftnchek has read, so that there is no
call tree, then ftnchek will look for any non-
library routines that are not called by any other
routine, and use these as substitutes for the main
program in constructing the call tree and deciding
what to check. If no such top-level non-library
routines are found, then all inter-module calls and
all COMMON declarations will be checked.)
See also: -arguments, -calltree, -common, -extern.
-list Specifies that a listing of the Fortran program is
to be printed out with line numbers. If ftnchek
detects an error, the error message follows the
program line with a caret ( ^ ) specifying the
location of the error. If no source listing was
requested, ftnchek will still print out any line
containing an error, to aid the user in determining
where the error occurred. Default = no.
See also: -symtab, -verbose.
-makedcls=num
Prepare a neatly-formatted file of declarations of
variables, common blocks, and namelist lists, for
possible merging into the source code. The decla-
rations are stored in a file of the same name as
the source code, but with the extension changed to
2 June 1995 12
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
.dcl. If no declarations are written to the file,
it is deleted to reduce clutter from empty files.
If input comes from standard input, instead of a
named file, then declarations are written to stan-
dard output.
Variables are declared in alphabetical order within
each declaration class and type, with integer vari-
ables first, because of their later possible use in
array dimensions.
PARAMETER statements are an exception to the alpha-
betical order rule, because the Fortran 77 Standard
requires that the expressions defining parameter
values refer only to constants and already-defined
parameter names. This forces the original source
file order of such statements to be preserved in
the declaration files.
Explicit declaration of all variables is considered
good modern programming practice. By using com-
piler options to reject undeclared variables, mis-
spelled variable names (or names extending past
column 72) can be caught at compile time. Explicit
declarations also greatly facilitate changing
floating-point precision with filters such as
dtoq(1L), dtos(1L), fd2s(1L), fs2d(1L), qtod(1L),
and stod(1L). These programs are capable of chang-
ing types of explicit floating-point type declara-
tions, intrinsic functions, and constants, but
because they do not carry out rigorous lexical and
grammatical analysis of the Fortran source code,
they cannot provide modified type declarations for
undeclared variables.
The setting values are given by the sum of selected
option values from the following list:
0: Do not write a declaration file.
1: Write a declaration file.
2: Normally, all variables are included in the
declaration file. With this option, include
only undeclared variables. This setting is
useful if you want to check for undeclared
variables, since Fortran source files with
all variables properly declared will not
result in a .dcl file. With this option,
common blocks and namelist lists will not be
included in the declaration file, since by
their nature they cannot be undeclared.
2 June 1995 13
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
4: The declarations are normally prettyprinted
to line up neatly in common columns, as in
the declaration files output by the Extended
PFORT Verifier, pfort(1L). This option value
selects instead compact output, without col-
umn alignment.
8: Causes continuation lines to be used where
permissible. The default is to begin a new
declaration on each line. This option is
appropriate to use with the option for com-
pact output.
16: Output Fortran keywords in lowercase, instead
of the default uppercase.
32: Output variables and constants in lowercase,
instead of the default uppercase. Character
string constants are not affected by this
option.
64: Omit declarations of internal integer vari-
ables produced by the SFTRAN3 preprocessor,
xsf3(1L), as part of the translation of
structured Fortran statements to ordinary
Fortran. These variables have six-character
names of the form NPRddd, NXdddd, N2dddd, and
N3dddd, where d is a decimal digit. Because
they are invisible in the SFTRAN3 source
code, and will change if the SFTRAN3 code is
modified, such variables should not be
explicitly declared. Instead, they should
just assume the default Fortran INTEGER data
type based on their initial letter, N.
128: Use an asterisk as the comment character; the
default is otherwise 'C'.
256: Use 'c' instead of 'C' or '*' as the comment
character.
If any non-zero value is specified, then declara-
tion output is selected, even if the value 1 was
not included in the sum.
The declaration files contain distinctive comments
that mark the start and end of declarations for
each program unit, to facilitate using text editor
macros for merging the declarations back into the
source code.
2 June 1995 14
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
-novice
This flag is intended to provide more helpful out-
put for beginners. It has two effects:
(a) provides an extra message to the effect that a
function that is used but not defined anywhere
might be an array which the user forgot to
declare in a DIMENSION statement (since the
syntax of an array reference is the same as
that of a function reference).
(b) modifies the form of the error messages and
warnings. If the flag is turned off by
-nonovice, these messages are printed in a
style more resembling UNIX lint.
Default = yes.
In versions of ftnchek prior to 2.6, this option
could take on various numerical values, as a way of
controlling various classes of warnings. These
warnings are now controlled individually by their
own flags. Novice level 1 is now handled by the
-array flag; level 2 has been eliminated; level 3
is equivalent now to setting -novice to yes; level
4 is handled by the -pure flag.
-output=filename
This setting is provided for convenience on sys-
tems which do not allow easy redirection of output
from programs. When this setting is given, the
output which normally appears on the screen will be
sent instead to the named file. Note, however,
that operational errors of ftnchek itself (e.g. out
of space or cannot open file) will still be sent to
the screen. The extension for the filename is
optional, and if no extension is given, the exten-
sion .lis will be used.
-portability
ftnchek will give warnings for a variety of non-
portable usages. Examples include the use of tabs
except in comments or inside strings, the use of
Hollerith constants, and the equivalencing of vari-
ables of different data types. This option does
not produce warnings for supported extensions to
the Fortran 77 Standard, which may also cause
portability problems. To catch those, use the -f77
option. Default = no.
2 June 1995 15
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
See also: -backslash, -f77, -hollerith, -pretty,
-wordsize.
-pretty
Controls certain messages related to the appear-
ance of the source code. These warn about things
that might be deceptive to the reader. Default =
yes.
The warnings controlled by this flag include such
things as comments that are interspersed among the
continuation lines of a statement, lack of space
between a keyword and a following variable name,
and statement lines containing characters past col-
umn 72.
See also: -f77, -portability.
-project
ftnchek will create a project file from each
source file that is input while this flag is in
effect. The project file will be given the same
name as the input file, but with the extension .f
or .for replaced by .prj. (If input is from stan-
dard input, the project file is named ftnchek.prj.)
Default = no.
A project file contains a summary of information
from the source file, for use in checking agreement
among FUNCTION, SUBROUTINE, and COMMON usages in
other files. It allows incremental checking, which
saves time whenever you have a large set of files
containing shared subroutines, most of which seldom
change. You can run ftnchek once on each file with
the -project flag set, creating the project files.
Usually you would also set the -library and -noex-
tern flags at this time, to suppress messages
relating to consistency with other files. Only
error messages pertaining to each file by itself
will be printed at this time. Thereafter, run
ftnchek without these flags on all the project
files together, to check consistency among the dif-
ferent files. All messages internal to the indi-
vidual files will now be omitted. Only when a file
is altered will a new project file need to be made
for it.
Naturally, when the -project flag is set, ftnchek
will not read project files as input.
2 June 1995 16
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
Project files contain only information needed for
checking agreement between files. This means that
a project file is of no use if all modules of the
complete program are contained in a single file.
A more detailed discussion is given in the section
on Using Project Files.
-pure Assume functions are ``pure'', i.e., they will not
have side effects by modifying their arguments or
variables in a COMMON block. When this flag is in
effect, ftnchek will base its determination of set
and used status of the actual arguments on the
assumption that arguments passed to a function are
not altered. It will also issue a warning if a
function is found to modify any of its arguments or
any COMMON variables. Default = yes.
When this flag is turned off, actual arguments
passed to functions will be handled the same way as
actual arguments passed to subroutines. This means
that ftnchek will assume that arguments may be mod-
ified by the functions. No warnings will be given
if a function is found to have side effects.
Because stricter checking is possible if functions
are assumed to be pure, you should turn this flag
off only if your program actually uses functions
with side effects.
-reference
Specifies that a who-calls-who table be printed.
This table lists each subprogram followed by a list
of the routines it calls. Default = no.
The reference list omits routines called by unused
library modules. Thus it contains the same infor-
mation as for the -calltree flag, namely the hier-
archy of subprogram calls, but printed in a differ-
ent format. This prints out a breadth-first
traversal of the call tree whereas -calltree prints
out a depth-first traversal. If both -calltree and
-reference flags are given, only the reference form
of the table will be produced.
See also: -calltree, -crossref, -library, -sort,
-symtab.
2 June 1995 17
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
-resource
Prints the amount of resources used by ftnchek in
processing the program. This listing may be useful
in analyzing the size and complexity of a program.
It can also help in choosing larger sizes for
ftnchek's internal tables if they are too small to
analyze a particular program. Default = no.
In this listing, the term ``chunk size'' is the
size of the blocks of memory allocated to store the
item in question, in units of the size of one item,
not necessarily in bytes. When the initially allo-
cated space is filled up, more memory is allocated
in chunks of this size. The following is an expla-
nation of the items printed:
Source lines processed:
Total number of lines of code, with separate
totals for statement lines and comment lines.
Comment lines include lines with 'C' or '*' in
column 1 as well as blank lines and lines con-
taining only an inline comment. Statement
lines are all other lines, including lines that
have an inline comment following some code.
Continuation lines are counted as separate
lines. Lines in include files are counted each
time the file is included.
Total executable statements:
Number of statements in the program, other than
specification, data, statement-function, FOR-
MAT, ENTRY, and END statements.
Total number of modules:
A module is any external subprogram, including
the main program, subroutines, functions, and
block data units. This count is of modules
defined within the source, not modules refer-
enced. Statement functions are not included.
A subprogram with multiple entry points is only
counted once.
Max identifier name chars:
Number of characters used for storing identi-
fier names. An identifier is a variable, sub-
program, or common block name. Local names are
those of local variables in a subprogram,
whereas global names refer to subprogram and
common block names, as well as dummy argument
names and common variable names. Actual argu-
ment text (up to 15 characters for each argu-
ment) is also included here. The space used
for local names is recovered at the end of each
module, whereas the global space grows until
2 June 1995 18
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
the whole program is analyzed. Unfortunately,
this figure may include some common block names
and arguments stored more than once, although a
heuristic is used that will avoid duplicates in
many cases.
Max token text chars:
A token is the smallest syntactic unit of the
FORTRAN language above the level of individual
characters. For instance a token can be a vari-
able name, a numerical constant, a quoted text
string, or a punctuation character. Token text
is stored while a module is being processed.
For technical reasons, single-character tokens
are not included in this total. Items that are
not represented in the symbol table may be
duplicated. The space for token text is recov-
ered at the end of each module, so this figure
represents the maximum for any one module.
Max local symbols:
This is the largest number of entries in the
local symbol table for any module. Local sym-
bol table entries include all variables and
parameters, common block names, statement func-
tions, external subprograms and intrinsic func-
tions referenced by the module. Literal con-
stants are not stored in the local symbol
table.
Max global symbols:
This is the number of entries in the global
symbol table at the end of processing. Global
symbol table entries include external subpro-
gram and common block names. Intrinsic func-
tions and statement functions are not included.
Max number of tokenlists:
A token list is a sequence of tokens represent-
ing the actual or dummy argument list of a sub-
program, or the list of variables in a common
block or namelist. Therefore this number rep-
resents the largest sum of COMMON, CALL,
NAMELIST and ENTRY statements and function
invocations for any one module. The space is
recovered at the end of each module.
Max token list/tree space:
This is the largest number of tokens in all the
token lists and token trees of any one module.
A token tree is formed when analyzing an
expression: each operand is a leaf of the tree,
and the operators are the nodes. Therefore
this number is a measure of the maximum
2 June 1995 19
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
complexity of an individual module. For
instance a module with many long arithmetic
expressions will have a high number. Note that
unlike token text described above, the number
of tokens is independent of the length of the
variable names or literal constants in the
expressions.
Number of subprogram invocations:
This is the sum over all modules of the number
of CALL statements and function invocations
(except intrinsic functions and statement func-
tions).
Number of common block decls:
This is the sum over all modules of the number
of common block declarations. That is, each
declaration of a block in a different module is
counted separately. (The standard allows mul-
tiple declarations of a block within the same
module; these are counted as only one declara-
tion since they are equivalent to a single long
declaration.)
Number of array dim & param ptrs:
This is the sum over all modules of the number
of array dimension and parameter definition
text strings saved for use by the -makedcls
option. The length of the text strings is not
counted. Each dimension of a multidimensional
array is counted separately.
These numbers are obviously not the same when pro-
ject files are used in place of the original source
code. Even the numbers for global entities may be
different, since some redundant information is
eliminated in project files.
-sixchar
One of the goals of the ftnchek program is to help
users to write portable Fortran programs. One
potential source of nonportability is the use of
variable names that are longer than six characters.
Some compilers just ignore the extra characters.
This behavior could potentially lead to two differ-
ent variables being considered as the same. For
instance, variables named AVERAGECOST and AVER-
AGEPRICE are the same in the first six characters.
If you wish to catch such possible conflicts, use
this flag. Default = no.
Use the -f77 flag if you want to list all variables
2 June 1995 20
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
longer than six characters, not just those pairs
that are the same in the first six.
See also: -f77, -portability.
-sort Specifies that a sorted list of all modules used
in the program be printed. This list is in ``pre-
requisite'' order, i.e. each module is printed only
after all the modules from which it is called have
been printed. This is also called a ``topological
sort'' of the call tree. Each module is listed
only once. Routines that are not in the call tree
of the main program are omitted. If there are any
cycles in the call graph (illegal in standard For-
tran) they will be detected and diagnosed. Default
= no.
See also: -calltree, -crossref, -reference,
-symtab.
-symtab
A symbol table will be printed out for each mod-
ule, listing all identifiers mentioned in the mod-
ule. This table gives the name of each variable,
its datatype, and the number of dimensions for
arrays. An asterisk (*) indicates that the vari-
able has been implicitly typed, rather than being
named in an explicit type declaration statement.
The table also lists all subprograms invoked by the
module, all COMMON blocks declared, etc. Default =
no.
See also: -calltree, -crossref, -list, -reference,
-sort.
-tab Accept DEC-style tab-formatted source. A line
beginning with an initial tab will be treated as a
new statement line unless the character after the
tab is a nonzero digit, in which case it is treated
as a continuation line. The next column after the
tab or continuation mark is taken as column 7. A
warning will be given in the case where the line is
a continuation, if -f77 is in effect. Default =
no.
2 June 1995 21
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
-truncation
Warn about possible truncation (or roundoff)
errors. Most of these are related to integer
arithmetic. The warnings enabled when this flag is
in effect are:
(a) use of the result of integer division where a
real result seems intended (namely as an expo-
nent, or if the quotient is later converted to
real);
(b) division in an integer constant expression that
yields a result of zero;
(c) exponentiation of an integer by a negative
integer (which yields zero unless the base
integer is 1 in magnitude);
(d) use of a non-integer array subscript or DO
index;
(e) conversion of any real type to integer, or con-
version of a complex value to real or integer;
(f) conversion of a double precision value to sin-
gle precision, or vice-versa (promotion). This
applies both to real types and to complex
types.
Default = yes.
Note: warnings about truncating type conversions
are given only when the conversion is done automat-
ically, e.g. by an assignment statement. If
intrinsic functions such as INT are used to perform
the conversion, no warning is given. Promotions of
real types from single to double precision are
included here because such conversions imply a pos-
sible loss of accuracy that is similar to the cor-
responding demotions.
See also: -portability, -wordsize.
-usage=num
Warn about unused or possible uninitialized vari-
ables and unused common blocks.
The meanings of the setting values are as follows:
0: no warnings.
1: warn if variables are (or may be) used before
2 June 1995 22
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
they are set.
2: warn if variables are declared or set but never
used.
3: give both types of warnings.
Default = 3.
Sometimes ftnchek makes a mistake about these warn-
ings. Usually it errs on the side of giving a
warning where no problem exists, but in rare cases
it may fail to warn where the problem does exist.
See the section on Bugs for examples. If variables
are equivalenced, the rule used by ftnchek is that
a reference to any variable implies the same refer-
ence to all variables it is equivalenced to. For
arrays, the rule is that a reference to any array
element is treated as a reference to all elements
of the array.
This setting controls warnings not only for local
variables but also for variables in COMMON blocks.
Level 2 also controls whether a warning is given
when an entire COMMON block is unused. When check-
ing for used-before-set errors involving COMMON
variables, ftnchek does not do a thorough enough
analysis of the calling sequence to know which rou-
tines are called before others. So warnings about
this type of error will only be given for cases in
which a variable is used in some routine but not
set in any other routine. Checking of individual
COMMON variables is done only if the -common set-
ting is 3 (variable by variable agreement).
See also: -common, -declare, -volatile.
-verbose
This option is on by default. Turning it off
reduces the amount of output relating to normal
operation, so that error messages are more appar-
ent. This option is provided for the convenience
of users who are checking large suites of files.
The eliminated output includes the names of project
files, and the message reporting that no syntax
errors were found. (Some of this output is turned
back on by the -list and -symtab options.) Default
= yes.
2 June 1995 23
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
-volatile
Assume that COMMON blocks are volatile. Default =
no.
Many Fortran programmers assume that variables,
whether local or in COMMON, are static, i.e. that
once assigned a value, they retain that value per-
manently until assigned a different value by the
program. However, in fact the Fortran 77 Standard
does not require this to be the case. Local vari-
ables may become undefined between activations of a
module in which they are declared. Similarly, COM-
MON blocks may become undefined if no module in
which they are declared is active. (The technical
term for this behavior is ``automatic'', but
ftnchek uses the word ``volatile'' since it is
clearer to the nonspecialist.) Only COMMON blocks
declared in a SAVE statement, or declared in the
main program or in a block data subprogram remain
defined as long as the program is running. Vari-
ables and COMMON blocks that can become undefined
at some point are called volatile.
If the -volatile flag is turned on, ftnchek will
warn you if it finds a volatile COMMON block. If,
at the same time, the -usage setting is 1 or 3
(check used before set), ftnchek will try to check
whether such a block can lose its defined status
between activations of the modules where it is
declared. ftnchek does not do a very good job of
this: the rule used is to see whether the block is
declared in two separated subtrees of the call
tree. For instance, this would be the case if two
modules, both called from the main program, shared
a volatile COMMON block. A block can also become
undefined between two successive calls of the same
subprogram, but ftnchek is not smart enough to tell
whether a subprogram can be called more than once,
so this case is not checked for.
The -volatile flag does not affect the way ftnchek
checks the usage of local variables.
See also: -common, -usage.
-wordsize=num
Specifies the default word size to be num bytes.
This is the size of logical and single-precision
numeric variables that are not given explicit pre-
cisions. Double-precision and complex variables
will be twice this value, and double complex vari-
ables four times. Explicit precisions for non-
2 June 1995 24
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
character variables are an extension to the Fortran
77 Standard, and are given by type declarations
such as REAL*8 X. Default = 4 bytes.
If you want to change the built-in default value of
this setting, compile ftnchek with the macro name
BpW (Bytes per Word) set to the desired default
value. This is not critical: the word size value
does not matter for checking standard-conforming
programs that do not declare explicit precisions
for non-character variables or store Hollerith data
in variables. This setting also does not affect
the default size of character variables, which is
always 1 byte. Hollerith constants also are
assumed to occupy 1 byte per character.
The word size is used to determine whether trunca-
tion occurs in assignment statements, and to catch
precision mismatches in subprogram argument lists
and common block lists. The exact warnings that
are issued will depend on the status of other
flags. Under both the -portability or -nowordsize
flags, any mixing of explicit with default preci-
sion objects (character expressions not included)
is warned about. This applies to arithmetic
expressions containing both types of objects, and
to subprogram arguments and COMMON variables.
Under the -truncation flag, a warning is given for
assignment of an expression to a shorter variable
of the same type, or for promotion of a lower pre-
cision value to higher precision in an arithmetic
expression or an assignment statement.
Giving a word size of 0, or equivalently, using
-nowordsize means that no default value will be
assumed. Use this instead of -portability if you
want to check only for those aspects of portability
related to mixing default and explicit precision,
for example to flag places where REAL*8 is treated
as equivalent to DOUBLE PRECISION.
See also: -portability, -truncation.
-wrap=col
Controls the wrapping of error messages. Long
error messages that would run past the specified
column will be broken up into separate lines
between the words of the message for better read-
ability. If turned off with -nowrap, each separate
error message will be printed on one line, leaving
it up to the display to wrap the message or trun-
cate it. Default = 79.
2 June 1995 25
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
CHANGING THE DEFAULTS
ftnchek includes a mechanism for changing the default
values of all options by defining environment variables.
When ftnchek starts up, it looks in its environment for
any variables whose names are composed by prefixing the
string FTNCHEK_ onto the uppercased version of the option
name. If such a variable is found, its value is used to
specify the default for the corresponding switch or set-
ting. In the case of settings (for example, the -common
strictness setting) the value of the environment variable
is read as the default setting value. In the case of
switches, the default switch will be taken as true or yes
unless the environment variable has the value 0 or NO. Of
course, command-line options will override these defaults
the same way as they override the built-in defaults.
Note that the environment variable name must be con-
structed with the full-length option name, which must be
in uppercase. For example, to make ftnchek print a source
listing by default, set the environment variable
FTNCHEK_LIST to 1 or YES or anything other than 0 or NO.
The names FTNCHEK_LIS (not the full option name) or
ftnchek_list (lower case) would not be recognized.
Here are some examples of how to set environment variables
on various systems. For simplicity, all the examples set
the default -list switch to YES.
1. UNIX, Bourne shell: $ FTNCHEK_LIST=YES; export
FTNCHEK_LIST
2. UNIX, C shell: % setenv FTNCHEK_LIST YES
3. VAX/VMS: $ DEFINE FTNCHEK_LIST YES
4. MSDOS: $ SET FTNCHEK_LIST=YES
USING PROJECT FILES
This section contains detailed information on how to use
project files most effectively, and how to avoid some pit-
falls.
Ordinarily, project files should be created with the
-library flag in effect. In this mode, the information
saved in the project file consists of all subprogram dec-
larations, all subprogram invocations not resolved by dec-
larations in the same file, and one instance of each COM-
MON block declaration. This is the minimum amount of
information needed to check agreement between files.
If the file contains more than one routine, there are some
2 June 1995 26
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
possible problems that can arise from creating the project
file in library mode, because the calling hierarchy among
routines defined within the file is lost. Also, if the
routines in the file make use of COMMON blocks that are
shared with routines in other files, there will not be
enough information saved for the correct checking of set
and used status of COMMON blocks and COMMON variables
according to the -usage setting. Therefore if you plan to
use project files when the -usage setting is nonzero
(which is the default situation), and if multiple routines
in one project file share COMMON blocks with routines in
other files, the project files should be created with the
-library flag turned off. In this mode, ftnchek saves,
besides the information listed above, one invocation of
each subprogram by any other subprogram in the same file,
and all COMMON block declarations. This means that the
project file will be larger than necessary, and that when
it is read in, ftnchek may repeat some inter-module checks
that it already did when the project file was created. If
each project file contains only one module, there is no
loss of information in creating the project files in
library mode.
Because of the possible loss of information entailed by
creating a project file with the -library flag in effect,
whenever that project file is read in later, it will be
treated as a library file regardless of the current set-
ting of the -library flag. On the other hand, a project
file created with library mode turned off can be read in
later in either mode.
Here is an example of how to use the UNIX make utility to
automatically create a new project file each time the cor-
responding source file is altered, and to check the set of
files for consistency. The example assumes that a macro
OBJS has been defined which lists all the names of object
files to be linked together to form the complete exe-
cutable program.
# tell make what a project file suffix is
.SUFFIXES: .prj
# tell make how to create a .prj file from a .f file
.f.prj:
ftnchek -project -noextern -library $<
# set up macro PRJS containing project filenames
PRJS= $(OBJS:.o=.prj)
# "make check" will check everything that has been changed.
check: $(PRJS)
ftnchek $(PRJS)
2 June 1995 27
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
AN EXAMPLE
The following simple Fortran program illustrates the mes-
sages given by ftnchek. The program is intended to accept
an array of test scores and then compute the average for
the series.
C AUTHORS: MIKE MYERS AND LUCIA SPAGNUOLO
C DATE: MAY 8, 1989
C Variables:
C SCORE -> an array of test scores
C SUM -> sum of the test scores
C COUNT -> counter of scores read in
C I -> loop counter
REAL FUNCTION COMPAV(SCORE,COUNT)
INTEGER SUM,COUNT,J,SCORE(5)
DO 30 I = 1,COUNT
SUM = SUM + SCORE(I)
30 CONTINUE
COMPAV = SUM/COUNT
END
PROGRAM AVENUM
C
C MAIN PROGRAM
C
C AUTHOR: LOIS BIGBIE
C DATE: MAY 15, 1990
C
C Variables:
C MAXNOS -> maximum number of input values
C NUMS -> an array of numbers
C COUNT -> exact number of input values
C AVG -> average returned by COMPAV
C I -> loop counter
C
PARAMETER(MAXNOS=5)
INTEGER I, COUNT
REAL NUMS(MAXNOS), AVG
COUNT = 0
DO 80 I = 1,MAXNOS
READ (5,*,END=100) NUMS(I)
COUNT = COUNT + 1
80 CONTINUE
100 AVG = COMPAV(NUMS, COUNT)
END
2 June 1995 28
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
The compiler gives no error messages when this program is
compiled. Yet here is what happens when it is run:
$ run average
70
90
85
<EOF>
$
What happened? Why didn't the program do anything? The
following is the output from ftnchek when it is used to
debug the above program:
$ ftnchek -list -symtab average
FTNCHEK Version 2.8 May 1995
File average.f:
1 C AUTHORS: MIKE MYERS AND LUCIA SPAGNUOLO
2 C DATE: MAY 8, 1989
3
4 C Variables:
5 C SCORE -> an array of test scores
6 C SUM -> sum of the test scores
7 C COUNT -> counter of scores read in
8 C I -> loop counter
9
10 REAL FUNCTION COMPAV(SCORE,COUNT)
11 INTEGER SUM,COUNT,J,SCORE(5)
12
13 DO 30 I = 1,COUNT
14 SUM = SUM + SCORE(I)
15 30 CONTINUE
16 COMPAV = SUM/COUNT
^
Warning near line 16 col 20: integer quotient expr converted to real
17 END
18
Module COMPAV: func: real
Variables:
Name Type Dims Name Type Dims Name Type Dims Name Type Dims
COMPAV real COUNT intg I intg* J intg
SCORE intg 1 SUM intg
2 June 1995 29
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
* Variable not declared. Type has been implicitly defined.
Warning: Variables declared but never referenced:
J
Warning: Variables may be used before set:
SUM
19
20 PROGRAM AVENUM
21 C
22 C MAIN PROGRAM
23 C
24 C AUTHOR: LOIS BIGBIE
25 C DATE: MAY 15, 1990
26 C
27 C Variables:
28 C MAXNOS -> maximum number of input values
29 C NUMS -> an array of numbers
30 C COUNT -> exact number of input values
31 C AVG -> average returned by COMPAV
32 C I -> loop counter
33 C
34
35 PARAMETER(MAXNOS=5)
36 INTEGER I, COUNT
37 REAL NUMS(MAXNOS), AVG
38 COUNT = 0
39 DO 80 I = 1,MAXNOS
40 READ (5,*,END=100) NUMS(I)
41 COUNT = COUNT + 1
42 80 CONTINUE
43 100 AVG = COMPAV(NUMS, COUNT)
44 END
Module AVENUM: prog
External subprograms referenced:
COMPAV: real*
Variables:
Name Type Dims Name Type Dims Name Type Dims Name Type Dims
AVG real COUNT intg I intg MAXNOS intg*
NUMS real 1
* Variable not declared. Type has been implicitly defined.
Warning: Variables set but never used:
AVG
2 June 1995 30
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
0 syntax errors detected in file average.f
6 warnings issued in file average.f
Subprogram COMPAV: argument data type mismatch
at position 1:
Dummy arg SCORE is type intg in module COMPAV line 10 file average.f
Actual arg NUMS is type real in module AVENUM line 43 file average.f
According to ftnchek, the program contains variables which
may be used before they are assigned an initial value, and
variables which are not needed. ftnchek also warns the
user that an integer quotient has been converted to a
real. This may assist the user in catching an unintended
roundoff error. Since the -symtab flag was given, ftnchek
prints out a table containing identifiers from the local
module and their corresponding datatype and number of
dimensions. Finally, ftnchek warns that the function COM-
PAV is not used with the proper type of arguments.
With ftnchek's help, we can debug the program. We can see
that there were the following errors:
1. SUM and COUNT should have been converted to real
before doing the division.
2. SUM should have been initialized to 0 before entering
the loop.
3. AVG was never printed out after being calculated.
4. NUMS should have been declared INTEGER instead of
REAL.
We also see that I, not J, should have been declared INTE-
GER in function COMPAV. Also, MAXNOS was not declared as
INTEGER, nor COMPAV as REAL, in program AVENUM. These are
not errors, but they may indicate carelessness. As it
happened, the default type of these variables coincided
with the intended type.
Here is the corrected program, and its output when run:
C AUTHORS: MIKE MYERS AND LUCIA SPAGNUOLO
C DATE: MAY 8, 1989
C
C Variables:
C SCORE -> an array of test scores
C SUM -> sum of the test scores
C COUNT -> counter of scores read in
C I -> loop counter
C
REAL FUNCTION COMPAV(SCORE,COUNT)
2 June 1995 31
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
INTEGER SUM,COUNT,I,SCORE(5)
C
SUM = 0
DO 30 I = 1,COUNT
SUM = SUM + SCORE(I)
30 CONTINUE
COMPAV = FLOAT(SUM)/FLOAT(COUNT)
END
C
C
PROGRAM AVENUM
C
C MAIN PROGRAM
C
C AUTHOR: LOIS BIGBIE
C DATE: MAY 15, 1990
C
C Variables:
C MAXNOS -> maximum number of input values
C NUMS -> an array of numbers
C COUNT -> exact number of input values
C AVG -> average returned by COMPAV
C I -> loop counter
C
C
INTEGER MAXNOS
PARAMETER(MAXNOS=5)
INTEGER I, NUMS(MAXNOS), COUNT
REAL AVG,COMPAV
COUNT = 0
DO 80 I = 1,MAXNOS
READ (5,*,END=100) NUMS(I)
COUNT = COUNT + 1
80 CONTINUE
100 AVG = COMPAV(NUMS, COUNT)
WRITE(6,*) 'AVERAGE =',AVG
END
$ run average
70
90
85
<EOF>
AVERAGE = 81.66666
$
With ftnchek's help, our program is a success!
INTERPRETING THE OUTPUT
The messages given by ftnchek include not only syntax
errors but also warnings and informational messages about
things that are legal Fortran but that may indicate errors
2 June 1995 32
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
or carelessness. Most of these messages can be turned off
by command-line options. Which option controls each mes-
sage depends on the nature of the condition being warned
about. See the descriptions of the command-line flags in
the previous sections, and of individual messages below.
Each message is prefixed with a word or phrase indicating
the nature of the condition and its severity.
``Error'' means a syntax error. The simplest kind of syn-
tax errors are typographical errors, for example unbal-
anced parentheses or misspelling of a keyword. This type
of error is caught by the parser and appears with the
description ``parse error'' or ``syntax error'' (depending
on whether the parser was built using GNU bison or UNIX
yacc respectively). This type of error message cannot be
suppressed. Be aware that this type of error often means
that ftnchek has not properly interpreted the statement
where the error occurs, so that its subsequent checking
operations will be compromised. You should eliminate all
syntax errors before proceeding to interpret the other
messages ftnchek gives.
``Warning: Nonstandard syntax'' indicates an extension to
Fortran that ftnchek supports but that is not according to
the Fortran 77 Standard. The extensions that ftnchek
accepts are described in the section on Extensions below.
One example is the DO ... ENDDO construction. If a pro-
gram uses these extensions, warnings will be given only if
the -f77 flag is set. The default is to give no warnings.
``Warning'' in other cases means a condition that is sus-
picious but that may or may not be a programming error.
Frequently these conditions are legal under the standard.
Some are illegal but do not fall under the heading of syn-
tax errors. Usage errors are one example. These refer to
the possibility that a variable may be used before it has
been assigned a value (generally an error), or that a
variable is declared but never used (harmless but may
indicate carelessness). The amount of checking for usage
errors is controlled by the -usage flag, which is set for
the maximum amount of checking by default.
Truncation warnings cover situations in which accuracy may
be lost unintentionally, for example when a double preci-
sion value is assigned to a real variable. These warnings
are controlled by the -truncation flag, which is on by
default.
``Nonportable usage'' warns about some feature that may
not be accepted by some compilers even though it is not
contrary to the Fortran 77 Standard, or that may cause the
program to perform differently on different platforms.
For example, equivalencing real and integer variables is
usually a non-portable practice. The use of extensions to
2 June 1995 33
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
the standard language is, of course, another source of
non-portability, but this is handled as a separate case.
To check a program for true portability, both the -porta-
bility and the -f77 flags should be used. They are both
turned off by default. The -wordsize setting is provided
to check only those nonportable usages that depend on a
particular machine wordsize.
``Possibly misleading appearance'' is used for legal con-
structions that may not mean what they appear to mean at
first glance. For example, Fortran is insensitive to
blank space, so extraneous space within variable names or
the lack of space between a keyword and a variable can
convey the wrong impression to the reader. These messages
can be suppressed by turning off the -pretty flag, which
is on by default.
Other messages that are given after all the files are pro-
cessed, and having to do with agreement between modules,
do not use the word ``warning'' but generally fall into
that category. Examples include type mismatches between
corresponding variables in different COMMON block declara-
tions, or between dummy and actual arguments of a subpro-
gram. These warnings are controlled by the -common and
-arguments settings respectively. By default both are set
for maximum strictness of checking.
Another group of warnings about conditions that are often
harmless refer to cases where the array properties of a
variable passed as a subprogram argument differ between
the two routines. For instance, an array element might be
passed to a subroutine that expects a whole array. This
is a commonly-used technique for processing single rows or
columns of two-dimensional arrays. However, it could also
indicate a programming error. The -array setting allows
the user to adjust the degree of strictness to be used in
checking this kind of agreement between actual and dummy
array arguments. By default the strictness is maximum.
``Oops'' indicates a technical problem, meaning either a
bug in ftnchek or that its resources have been exceeded.
The format of the error messages has been modified from
previous versions for more clarity. The syntax error mes-
sages and warnings now have the filename included along
with the line number and column number. ftnchek now has
two different options for the appearance of these error
messages. If -novice is in effect, which is the default,
the messages are very similar in style to those of the
previous version. (In default style, the filename is not
printed in messages within the body of the program if
-list is in effect.) The other style of error messages is
selected by the -nonovice option. In this style, the
appearance of the messages is similar to that of the UNIX
2 June 1995 34
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
lint program.
ftnchek is still blind to some kinds of syntax errors.
The two most important ones are detailed checking of FOR-
MAT statements, and almost anything to do with control of
execution flow by means of IF, DO, and GOTO statements:
namely correct nesting of control structures, matching of
opening statements such as IF ... THEN with closing state-
ments such as ENDIF, and the proper use of statement
labels (numbers). Most compilers will catch these errors.
See the section on Limitations for a more detailed discus-
sion.
If ftnchek gives you a syntax error message when the com-
piler does not, it may be because your program contains an
extension to standard Fortran which is accepted by the
compiler but not by ftnchek. (See the section on Exten-
sions.) On a VAX/VMS system, you can use the compiler
option /STANDARD to cause the compiler to accept only
standard Fortran. On most UNIX or UNIX-like systems, this
can be accomplished by setting the flag -ansi. Also, con-
sult the README file included in the ftnchek distribution
for information on how to control which extensions ftnchek
accepts.
Many of the messages given by ftnchek are self-
explanatory. Those that need some additional explanation
are listed below in alphabetical order.
Common block NAME: data type mismatch at position n
The n-th variable in the COMMON block differs in
data type in two different declarations of the COM-
MON block. By default (-common strictness level
3), ftnchek is very picky about COMMON blocks: the
variables listed in them must match exactly by data
type and array dimensions. That is, the legal pair
of declarations in different modules:
COMMON /COM1/ A,B
and
COMMON /COM1/ A(2)
will cause ftnchek to give warnings at strictness
level 3. These two declarations are legal in For-
tran since they both declare two real variables.
At strictness level 1 or 2, no warning would be
given in this example, but the warning would be
given if there were a data type mismatch, for
instance, if B were declared INTEGER. Controlled
by -common setting.
2 June 1995 35
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
Common block NAME has long data type following short data
type
Some compilers require alignment of multi-byte
items so that each item begins at an address that
is a multiple of the item size. Thus if a short
(e.g. single-precision real) item is followed by a
long (e.g. double precision real) item, the latter
may not be aligned correctly. Controlled by
-portability option.
Common block NAME has mixed character and non-character
variables
The ANSI standard requires that if any variable in
a COMMON block is of type CHARACTER, then all other
variables in the same COMMON block must also be of
type CHARACTER. Controlled by -f77 option.
Common block NAME: varying length
For -common setting level 2, this message means
that a COMMON block is declared to have different
numbers of words in two different subprograms. A
word is the amount of storage occupied by one inte-
ger or real variable. For -common setting level 3,
it means that the two declarations have different
numbers of variables, where an array of any size is
considered one variable. This is not necessarily
an error, but it may indicate that a variable is
missing from one of the lists. Note that according
to the Fortran 77 Standard, it is an error for
named COMMON blocks (but not blank COMMON) to dif-
fer in number of words in declarations in different
modules. Given for -common setting 2 or 3.
Error: Badly formed logical/relational operator or con-
stant
Error: Badly formed real constant
The syntax analyzer has found the start of one of
the special words that begin and end with a period
(e.g. .EQ.), or the start of a numeric constant,
but did not succeed in finding a complete item of
that kind.
Error: cannot be adjustable size in module NAME
A character variable cannot be declared with a size
that is an asterisk in parentheses unless it is a
dummy argument, a parameter, or the name of the
function defined in the module.
2 June 1995 36
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
Error: cannot be declared in SAVE statement in module NAME
Only local variables and common blocks can be
declared in a SAVE statement.
Error: No path to this statement
ftnchek will detect statements which are ignored or
by-passed because there is no foreseeable route to
the statement. For example, an unnumbered state-
ment (a statement without a statement label),
occurring immediately after a GOTO statement, can-
not possibly be executed.
Error: Parse error
This means that the parser, which analyzes the For-
tran program into expressions, statements, etc.,
has been unable to find a valid interpretation for
some portion of a statement in the program. If
your compiler does not report a syntax error at the
same place, the most common explanations are: (1)
use of an extension to ANSI standard Fortran that
is not recognized by ftnchek, or (2) the statement
requires more lookahead than ftnchek uses (see sec-
tion on Bugs).
NOTE: This message means that the affected state-
ment is not interpreted. Therefore, it is possible
that ftnchek's subsequent processing will be in
error, if it depends on any matters affected by
this statement (type declarations, etc.).
Error: Statement out of order.
ftnchek will detect statements that are out of the
sequence specified for ANSI standard Fortran 77.
Table 1 illustrates the allowed sequence of state-
ments in the Fortran language. Statements which
are out of order are nonetheless interpreted by
ftnchek, to prevent ``cascades'' of error messages.
--------------------------------------------------------
| | implicit
| parameter |---------------------
| | other specification
format |---------------|---------------------
and | | statement-function
entry | data |---------------------
| | executable
--------------------------------------------------------
Table 1
2 June 1995 37
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
Error: Syntax error
This is the same as ``Error: Parse error'' (see
above). It is generated if your version of ftnchek
was built using the UNIX yacc parser generator
rather than GNU bison.
Identifiers which are not unique in first six chars
Warns that two identifiers which are longer than 6
characters do not differ in the first 6 characters.
This is for portability: they may not be considered
distinct by some compilers. Controlled by -sixchar
option.
Nonportable usage: argument precision may not be
correct for intrinsic function
The precision of an argument passed to an intrinsic
function may be incorrect on some computers.
Issued when a numeric variable declared with
explicit precision (e.g. REAL*8 X) is passed to a
specific intrinsic function (e.g. DSQRT(X)). Con-
trolled by -portability and -wordsize.
Nonportable usage: character constant/variable length
exceeds 255
Some compilers do not support character strings
more than 255 characters in length. Controlled by
-portability.
Nonportable usage: File contains tabs
ftnchek expands tabs to be equivalent to spaces up
to the next column which is a multiple of 8. Some
compilers treat tabs differently, and also it is
possible that files sent by electronic mail will
have the tabs converted to blanks in some way.
Therefore files containing tabs may not be compiled
correctly after being transferred. ftnchek does
not give this message if tabs only occur within
comments or character constants. Controlled by
-portability.
Nonportable usage: non-integer DO loop bounds
This warning is only given when the DO index and
bounds are non-integer. Use of non-integer quanti-
ties in a DO statement may cause unexpected errors,
or different results on different machines, due to
roundoff effects. Controlled by -portability.
2 June 1995 38
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
Possibly it is an array which was not declared
This message is appended to warnings related to a
function invocation or to an argument type mis-
match, for which the possibility exists that what
appears to be a function is actually meant to be an
array. If the programmer forgot to dimension an
array, references to the array will be interpreted
as function invocations. This message will be sup-
pressed if the name in question appears in an
EXTERNAL or INTRINSIC statement. Controlled by the
-novice option.
Possibly misleading appearance: characters past 72 columns
The program is being processed with the statement
field width at its standard value of 72, and some
nonblank characters have been found past column 72.
In this case, ftnchek is not processing the charac-
ters past column 72, and is notifying the user that
the statement may not have the meaning that it
appears to have. These characters might be
intended by the programmer to be significant, but
they will be ignored by the compiler. (A similar
warning is alternatively given under the -f77 flag
if the -columns setting is used to increase the
statement field width.) Controlled by -pretty.
Possibly misleading appearance: Common block declared
in more than one statement
Such multiple declarations are legal and have the
same effect as a continuation of the original dec-
laration of the block. This warning is only given
if the two declarations are separated by one or
more intervening statements. Controlled by
-pretty.
Possibly misleading appearance: Continuation follows
comment or blank line
ftnchek issues this warning message to alert the
user that a continuation of a statement is inter-
spersed with comments, making it easy to overlook.
Controlled by -pretty.
Possibly misleading appearance: Extraneous parentheses
Warns about parentheses surrounding a variable by
itself in an expression. When a parenthesized
variable is passed as an argument to a subprogram,
it is treated as an expression, not as a variable
whose value can be modified by the called routine.
Controlled by -pretty.
2 June 1995 39
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
Subprogram NAME: argument data type mismatch at position n
The subprogram's n-th actual argument (in the CALL
or the usage of a function) differs in datatype or
precision from the n-th dummy argument (in the SUB-
ROUTINE or FUNCTION declaration). For instance, if
the user defines a subprogram by
SUBROUTINE SUBA(X)
REAL X
and elsewhere invokes SUBA by
CALL SUBA(2)
ftnchek will detect the error. The reason here is
that the number 2 is integer, not real. The user
should have said
CALL SUBA(2.0)
When checking an argument which is a subprogram,
ftnchek must be able to determine whether it is a
function or a subroutine. The rules used by
ftnchek to do this are as follows: If the subpro-
gram, besides being passed as an actual argument,
is also invoked directly elsewhere in the same mod-
ule, then its type is determined by that usage. If
not, then if the name of the subprogram does not
appear in an explicit type declaration, it is
assumed to be a subroutine; if it is explicitly
typed it is taken as a function. Therefore, sub-
routines passed as actual arguments need only be
declared by an EXTERNAL statement in the calling
module, whereas functions must also be explicitly
typed in order to avoid generating this error mes-
sage.
Controlled by -arguments.
Subprogram NAME: argument arrayness mismatch at position n
Similar to the preceding situation, but the subpro-
gram dummy argument differs from the corresponding
actual argument in its number of dimensions or num-
ber of elements. Controlled by -array together
with -arguments.
Subprogram NAME: argument mismatch at position n
A character dummy argument is larger than the cor-
responding actual argument, or a Hollerith dummy
2 June 1995 40
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
argument is larger than the corresponding actual
argument. Controlled by -arguments.
Subprogram NAME: argument usage mismatch
ftnchek detects a possible conflict between the way
a subprogram uses an argument and the way in which
the argument is supplied to the subprogram. The
conflict can be one of two types, as outlined
below.
Dummy arg is modified, Actual arg is const or expr
A dummy argument is an argument as named in a SUB-
ROUTINE or FUNCTION statement and used within the
subprogram. An actual argument is an argument as
passed to a subroutine or function by the caller.
ftnchek is saying that a dummy argument is modified
by the subprogram, implying that its value is
changed in the calling module. The corresponding
actual argument should not be a constant or expres-
sion, but rather a variable or array element which
can be legitimately assigned to. Given for -usage
setting 1 or 3.
Dummy arg used before set, Actual arg not set
Here a dummy argument may be used in the subprogram
before having a value assigned to it by the subpro-
gram. The corresponding actual argument should
have a value assigned to it by the caller prior to
invoking the subprogram. Given for -usage setting
1 or 3.
These warnings are not affected by the -arguments
setting.
Subprogram NAME invoked inconsistently
Here the mismatch is between the datatype of the
subprogram itself as used and as defined. For
instance, if the user declares
INTEGER FUNCTION COUNT(A)
and invokes COUNT in another module as
N = COUNT(A)
without declaring its datatype, it will default to
real type, based on the first letter of its name.
The calling module should have included the
2 June 1995 41
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
declaration
INTEGER COUNT
Given for -arguments setting 2 or 3.
Subprogram NAME: varying length argument lists:
An inconsistency has been found between the number
of dummy arguments (parameters) a subprogram has
and the number of actual arguments given it in an
invocation. ftnchek keeps track of all invocations
of subprograms (CALL statements and expressions
using functions) and compares them with the defini-
tions of the subprograms elsewhere in the source
code. The Fortran compiler normally does not catch
this type of error. Given for -arguments setting 1
or 3.
Variable not declared. Type has been implicitly defined
When printing the symbol table for a module,
ftnchek will flag with an asterisk all identifiers
that are not explicitly typed and will show the
datatype that was assigned through implicit typing.
This provides support for users who wish to declare
all variables as is required in Pascal or some
other languages. This message appears only when
the -symtab option is in effect. Alternatively,
use the -declare flag if you want to get a list of
all undeclared variables.
Variables declared but never referenced
Detects any identifiers that were declared in your
program but were never used, either to be assigned
a value or to have their value accessed. Variables
in COMMON are excluded. Given for -usage setting 2
or 3.
Variables set but never used
ftnchek will notify the user when a variable has
been assigned a value, but the variable is not oth-
erwise used in the program. Usually this results
from an oversight. Given for -usage setting 2 or
3.
Variables used before set
This message indicates that an identifier is used
to compute a value prior to its initialization.
Such usage may lead to an incorrect value being
2 June 1995 42
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
computed, since its initial value is not con-
trolled. Given for -usage setting 1 or 3.
Variables may be used before set
Similar to used before set except that ftnchek is
not able to determine its status with certainty.
ftnchek assumes a variable may be used before set
if the first usage of the variable occurs prior in
the program text to its assignment. Given for
-usage setting 1 or 3.
Warning: DO index is not integer
This warning is only given when the DO bounds are
integer, but the DO index is not. It may indicate
a failure to declare the index to be an integer.
Controlled by -truncation option.
Warning: integer quotient expr converted to real
The quotient of two integers results in an integer
type result, in which the fractional part is
dropped. If such an integer expression involving
division is later converted to a real datatype, it
may be that a real type division had been intended.
Controlled by -truncation option.
Warning: Integer quotient expr used in exponent
The quotient of two integers results in an integer
type result, in which the fractional part is
dropped. If such an integer expression is used as
an exponent, it is quite likely that a real type
division was intended. Controlled by -truncation
option.
Warning: NAME not set when RETURN encountered
The way that functions in Fortran return a value is
by assigning the value to the name of the function.
This message indicates that the function was not
assigned a value before the point where a RETURN
statement was found. Therefore it is possible that
the function could return an undefined value.
Warning: Nonstandard syntax: adjustable size cannot be
concate- nated here
The Fortran 77 Standard forbids concatenating char-
acter variables whose size is an asterisk in paren-
theses, except in an assignment statement. Con-
trolled by -f77.
2 June 1995 43
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
Warning: Nonstandard syntax: characters past 72 columns
A statement has been read which has nonblank char-
acters past column 72, with the statement field
extended beyond the standard value of 72 columns by
the -col setting. Standard Fortran ignores all
text in those columns, but some compilers do not.
Thus the program may be treated differently by dif-
ferent compilers. Controlled by -f77 option and
-columns setting.
Warning: Possible division by zero
This message is printed out wherever division is
done (except division by a constant). Use it to
help locate a runtime division by zero problem.
Controlled by -division option.
Warning: real truncated to intg
ftnchek has detected an assignment statement which
has a real expression on the right, but an integer
variable on the left. The fractional part of the
real value will be lost. If you explicitly convert
the real expression to integer using the INT or
NINT intrinsic function, no warning will be
printed. A similar message is printed if a double
precision expression is assigned to a single preci-
sion variable, etc. Controlled by -truncation
option.
Warning: subscript is not integer
Since array subscripts are normally integer quanti-
ties, the use of a non-integer expression here may
signal an error. Controlled by -truncation option.
Warning: Unknown intrinsic function
This message warns the user that a name declared in
an INTRINSIC statement is unknown to ftnchek.
Probably it is a nonstandard intrinsic function,
and so the program will not be portable. The func-
tion will be treated by ftnchek as a user-defined
function. This warning is not controlled by any
option, since it affects ftnchek's analysis of the
program.
LIMITATIONS AND EXTENSIONS
ftnchek accepts ANSI standard Fortran-77 programs with
some minor limitations and numerous common extensions.
Limitations:
2 June 1995 44
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
ftnchek uses only one line of lookahead when ana-
lyzing a program into its basic syntactic elements.
If a particular statement is difficult to identify,
it may be handled improperly if the ambiguity is
not resolved on a single line. This limitation
applies to complex constants except in DATA state-
ments, and to situations in which a variable name
might be confused with a keyword. For example, if
the variable name WRITE is used for an array, then
a very long statement assigning a value to some
element of this array could be mistaken as a WRITE
statement if the equals sign is not on the same
line as the word WRITE.
The dummy arguments in statement functions are
treated like ordinary variables of the program.
That is, their scope is the entire module, not just
the statement function definition.
The checking of FORMAT statements is lax, tolerat-
ing missing separators (comma, etc.) between format
descriptors in places where the Standard requires
them, and allowing .d fields on descriptors that
should not have them. It does warn under -f77
about nonstandard descriptor types (like O), and
supported extensions.
The only checking related to control of execution
flow is a warning about statements that cannot be
reached because they do not have a label and they
follow an unconditional transfer. There is no
checking for correct nesting of DO loops or match-
ing of opening statements such as IF ... THEN with
closing statements such as ENDIF, nor the proper
definition and use of statement labels. Fortu-
nately, most compilers will catch these errors.
If a user-supplied subprogram has the same name as
one of the nonstandard intrinsic functions, it must
be declared in an EXTERNAL statement in any routine
that invokes it. Otherwise it will be subject to
the checking normally given to the intrinsic func-
tion. Since the nonstandard intrinsics are not
standard, this EXTERNAL statement is not required
by the Fortran 77 Standard. See the lists of sup-
ported nonstandard intrinsic functions under Exten-
sions below.
Extensions:
All of these extensions (except lower-case charac-
ters) will generate warnings if the -f77 flag is
set. Some of the extensions listed below are part
of the Fortran-90 Standard. These are indicated by
the notation (F90).
2 June 1995 45
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
Tabs are permitted, and translated into equivalent
blanks which correspond to tab stops every 8
columns. The standard does not recognize tabs.
Note that some compilers allow tabs, but treat them
differently. The treatment defined for DEC FORTRAN
can be achieved using the -tab option.
Strings may be delimited by either quote marks or
apostrophes. A sequence of two delimiter charac-
ters is interpreted as a single embedded delimiter
character. (F90)
Strings may contain UNIX-style backslash escape
sequences. They will be interpreted as such if the
-backslash flag is set. Otherwise the backslash
character will be treated as a normal printing
character.
Lower case characters are permitted, and are con-
verted internally to uppercase except in character
strings. The standard specifies upper case only,
except in comments and strings. (F90)
Hollerith constants are permitted, in accordance
with the Fortran 77 Standard, appendix C. They
should not be used in expressions, or confused with
datatype CHARACTER.
The letter 'D' (upper or lower case) in column 1 is
treated as the beginning of a comment. There is no
option to treat such lines as statements instead of
comments.
Statements may be longer than 72 columns provided
that the setting -column was used to increase the
limit. According to the standard, all text from
columns 73 through 80 is ignored, and no line may
be longer than 80 columns.
Variable names may be longer than six characters.
The standard specifies six as the maximum. ftnchek
permits names up to 31 characters long (F90).
Variable names may contain underscores and dollar
signs, which are treated the same as alphabetic
letters. The default type for variables beginning
with these characters is REAL. In IMPLICIT type
statements specifying a range of characters, the
dollar sign follows Z and is followed by under-
score. Fortran 90 permits underscores in variable
names.
The UNIX version tolerates the presence of prepro-
cessor directives, namely lines beginning with the
2 June 1995 46
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
pound sign (#). These are treated as comments,
except for #line directives, which are interpreted,
and are used to set the line number and source file
name for warnings and error messages. Note that
#include directives are not processed by ftnchek.
Programs that use them for including source files
should be passed through the preprocessor before
being input to ftnchek. As noted below, ftnchek
does process INCLUDE statements, which have a dif-
ferent syntax.
The DO ... ENDDO control structure is permitted.
The syntax which is recognized is according to
either of the following two forms:
DO [label [,]] var = expr , expr [, expr]
...
END DO
or
DO [label [,]] WHILE ( expr )
...
END DO
where square brackets indicate optional elements.
This is a subset of the Fortran 90 do-loop syntax.
The ACCEPT and TYPE statements (for terminal I/O)
are permitted, with the same syntax as PRINT.
Statements may have any number of continuation
lines. The standard allows a maximum of 19.
Inline comments, beginning with an exclamation
mark, are permitted. (F90)
NAMELIST I/O is supported. The syntax is the same
as in Fortran 90.
FORMAT statements can contain a dollar sign to
indicate suppression of carriage-return. An inte-
ger expression enclosed in angle brackets can be
used anywhere in a FORMAT statement where the For-
tran 77 Standard allows an integer constant (except
for the length of a Hollerith constant), to provide
a run-time value for a repeat specification or
field width.
The IMPLICIT NONE statement is supported. The
meaning of this statement is that all variables
must have their data types explicitly declared.
Rather than flag the occurrences of such variables
with syntax error messages, ftnchek waits till the
end of the module, and then prints out a list of
all undeclared variables, as it does for the
-declare option. (F90)
2 June 1995 47
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
Data types INTEGER, REAL, COMPLEX, and LOGICAL are
allowed to have an optional precision specification
in type declarations. For instance, REAL*8 means
an 8-byte floating point data type. The REAL*8
datatype is not necessarily considered equivalent
to DOUBLE PRECISION, depending on the -wordsize
setting. The Fortran 77 Standard allows a length
specification only for CHARACTER data.
ftnchek supports the DOUBLE COMPLEX type specifica-
tion for a complex quantity whose real and imagi-
nary parts are double precision. Mixed-mode arith-
metic involving single-precision complex with dou-
ble-precision real data, prohibited under the Stan-
dard, yields a double complex result. The double
complex counterparts of all the standard intrinsic
functions for complex data are included:
DCMPLX DCONJG DIMAG DREAL IMAG
CDABS CDSQRT CDEXP CDLOG CDSIN CDCOS
ZABS ZSQRT ZEXP ZLOG ZSIN ZCOS
The following other commonly found nonstandard
intrinsic functions are provided. All except EXIT
and LOC are defined in MIL-STD 1753.
BTEST IAND IOR IBSET IBCLR
IBITS IEOR ISHFT ISHFTC NOT
EXIT LOC
For the UNIX version of ftnchek, the following com-
mon UNIX intrinsic functions are provided:
ABORT AND GETARG GETENV GMTIME
IARGC LSHIFT LTIME OR IRAND
RAND RSHIFT SRAND SYSTEM TIME
XOR
Note: there are two common calling sequences for
RAND and IRAND: with zero arguments or with 1 argu-
ment. By default, ftnchek accepts either form. If
you wish to enforce strict adherence to one form or
the other, you should compile ftnchek with one of
the two macros RAND_NO_ARG or RAND_ONE_ARG set.
For the VAX/VMS version of ftnchek, the following
common VMS intrinsic functions are provided:
DATE ERRSNS IDATE RAN SECNDS
SIZEOF TIME
2 June 1995 48
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
Argument checking is not tight for those nonstan-
dard intrinsics that take arrays or mixed argument
types.
ftnchek permits the INCLUDE statement, which causes
inclusion of the text of the given file. The syn-
tax is
INCLUDE 'filename'
This is compatible with Fortran 90. When compiled
for VMS, ftnchek will assume a default extension of
.for if no filename extension is given. Also for
compatibility with VMS, the VMS version allows the
qualifier /[NO]LIST following the filename, to con-
trol the listing of the included file. There is no
support for including VMS text modules.
In diagnostic output relating to items contained in
include files, the location of the error is speci-
fied by both its location in the include file and
the location in the parent file where the file was
included.
ftnchek accepts PARAMETER definitions that involve
intrinsic functions and exponentiation by a non-
integer exponent. Both of these cases are prohib-
ited by the Fortran 77 Standard, and will be warned
about if the -f77 flag is set. If an intrinsic
function is a compile-time integer constant,
ftnchek will evaluate it. This allows better
checking if the parameter is used in declaring
array sizes. Fortran 90 allows intrinsic functions
in PARAMETER definitions.
The intrinsic functions that are evaluated are:
ABS IABS DIM IDIM MAX
MAX0 MIN MIN0 MOD SIGN
ISIGN LEN ICHAR INDEX
The functions of integer arguments are evaluated
only if the arguments are integer constant expres-
sions. (These may involve integer constants,
parameters, and evaluated intrinsic functions.)
The function LEN is evaluated if its argument is an
expression involving only character constants and
variables whose length is not adjustable. The
functions ICHAR and INDEX are evaluated only if the
arguments are character constants. ftnchek gives a
warning if it needs the value of some intrinsic
function that is not evaluated.
2 June 1995 49
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
NEW FEATURES
Here are the changes from Version 2.7 to Version 2.8:
1. Improvements in handling command-line settings: add
support for colon as assignment operator, and extend
setting switch support to include a default value to
replace out-of-range values, instead of just choosing
the nearer endpoint of the valid range.
2. New options: -makedcls=num to generate variable decla-
rations; -backslash to handle UNIX-style backslash
escapes in character strings; -resource to print out
internal resource usage; -tab to accept DEC-style tab-
formatted source.
3. New extensions to syntax: Accept quote marks as an
alternative to apostrophes for delimiting strings.
Accept 'D' as equivalent to 'C' in column 1 for com-
ments. A patch is supplied to allow ``Cray pointer''
syntax to be tolerated. (This patch does not include
checking proper use of pointers.)
4. Provide variable names and not just position numbers
in warnings about mismatches in common block declara-
tions and subprogram argument lists.
5. Add installation validation suite to check for correct
functioning after a new installation, or a new compi-
lation with a different compiler or compiler options.
The validation suite also serves to record input cases
that exhibited bugs in older versions of the program,
providing regression testing to ensure that changes do
not introduce new bugs, or restore old ones. This
test suite uncovered compiler optimizer errors on at
least one system, errors which did not appear in older
versions of ftnchek.
6. Improve memory management to avoid running out of
space.
7. Update the UNIX Makefile with new targets following
the Free Software Foundation standards, and create the
CHECKLIST file to record systems for which this ver-
sion of ftnchek has been successfully built and has
passed the validation suite tests.
8. Add the man2ps script, and a target in the UNIX Make-
file to use it for converting the manual pages file to
PostScript.
9. Correct several small typographical irregularities in
these manual pages. troff preserves all input spaces,
so great care is needed in preparing troff input to
avoid introducing spurious space into the typeset
2 June 1995 50
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
output.
Grateful acknowledgement is given to Nelson H. F. Beebe of
the University of Utah for providing most of these
improvements, and especially for writing most of the new
code to produce variable declarations, which represents a
very substantial effort.
Here are the changes from Version 2.6 to Version 2.7:
1. Fixed bugs: to allow statement functions with no argu-
ments; to catch extra comma in subprogram argument
lists; argument of LEN does not need to have a defined
value.
2. Insensitive to blanks as per the Standard.
3. Changed behavior of options: -f77 controls warnings
about statement out of order and COMMON block with
mixed character and non-character data; -help option
now lists patch level and copyright; -novice controls
appearance of warning messages.
4. Added handling of explicit precision and double com-
plex data type. REAL*8 is no longer synonymous with
DOUBLE PRECISION, depending on the machine wordsize.
Checking length agreement for character data also done
properly now.
5. Checking usage status of COMMON blocks and COMMON
variables.
6. Improved format of messages.
7. Support for common nonstandard intrinsic functions.
8. New options: -arguments, -crossref, -reference, -sort,
-volatile, -wordsize, and -wrap.
9. Behavior when no top-level non-library modules found,
changed from no cross-checking to complete cross-
checking.
10. Added expansion of wildcards for filenames on the com-
mand line to the VMS and MS-DOS versions.
11. Parser is generated by bison. Formerly yacc was used.
12. Made changes to allow the IBM PC version handle larger
files.
BUGS
ftnchek still has much room for improvement. Your feed-
back is appreciated. We want to know about any bugs you
2 June 1995 51
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
notice. Bugs include not only cases in which ftnchek
issues an error message where no error exists, but also if
ftnchek fails to issue a warning when it ought to. Note,
however, that ftnchek is not intended to catch all syntax
errors (see section on Limitations). Also, it is not con-
sidered a bug for a variable to be reported as used before
set, if the reason is that the usage of the variable
occurs prior in the text to where the variable is set.
For instance, this could occur when a GOTO causes execu-
tion to loop backward to some previously skipped state-
ments. ftnchek does not analyze the program flow, but
assumes that statements occurring earlier in the text are
executed before the following ones.
We especially want to know if ftnchek crashes for any rea-
son. It is not supposed to crash, even on programs with
syntax errors. Suggestions are welcomed for additional
features which you would find useful. Tell us if any of
ftnchek's messages are incomprehensible. Comments on the
readability and accuracy of this document are also wel-
come.
You may also suggest support for additional extensions to
the Fortran language. These will be included only if it
is felt that the extensions are sufficiently widely
accepted by compilers.
If you find a bug in ftnchek, first consult the list of
known bugs below to see if it has already been reported.
Also check the section entitled ``Limitations and Exten-
sions'' above for restrictions that could be causing the
problem. If you do not find the problem documented in
either place, then send a report including
1. The operating system and CPU type on which ftnchek is
running.
2. The version of ftnchek.
3. A brief description of the bug.
4. If possible, a small sample program showing the bug.
The report should be sent to either of the following
addresses:
MONIOT@FORDMULC.BITNET
moniot@mary.fordham.edu
Highest priority will be given to bugs which cause ftnchek
to crash. Bugs involving incorrect warnings or error
2 June 1995 52
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
messages may take longer to fix.
Certain problems that arise when checking large programs
can be fixed by increasing the sizes of the data areas in
ftnchek. (These problems are generally signaled by error
messages beginning with ``Oops''.) The simplest way to
increase the table sizes is by recompiling ftnchek with
the LARGE_MACHINE macro name defined. Consult the make-
file and README file for the method of doing this.
The following is a list of known bugs.
1. Bug: Used-before-set message is suppressed for any
variable which is used as the loop index in an
implied-do loop, even if it was in fact used before
being set in some earlier statement. For example,
consider J in the statement
WRITE(5,*) (A(J), J=1,10)
Here ftnchek parses the I/O expression, A(J), where J
is used, before it parses the implied loop where J is
set. Normally this would cause ftnchek to report a
spurious used-before-set warning for J. Since this
report is usually in error and occurs fairly commonly,
ftnchek suppresses the warning for J altogether.
Prognosis: A future version of ftnchek is planned
which will handle implied-do loops correctly.
2. Bug: Variables used (not as arguments) in statement-
function subprograms do not have their usage status
updated when the statement function is invoked.
Prognosis: To be fixed in a future version of ftnchek.
3. Bug: VAX version does not expand wildcards in file-
names on the command line if they are followed without
space by an option, e.g. ftnchek *.f/calltree would
not expand the *.f. This is because VMS-style options
without intervening space are not supported by the GNU
shell_mung routine that is used to expand wildcards.
Prognosis: unlikely to be fixed.
ACKNOWLEDGEMENTS
ftnchek is a public-domain program. It was designed by
Dr. Robert Moniot, professor at Fordham University. Dur-
ing the academic year of 1988-1989, Michael Myers and
Lucia Spagnuolo developed the program to perform the
2 June 1995 53
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
variable usage checks. During the following year it was
augmented by Lois Bigbie to check subprogram arguments and
COMMON block declarations. Brian Downing assisted with
the implementation of the INCLUDE statement. John Quinn
wrote the common block usage checks. Nelson H. F. Beebe
of the University of Utah added most of the new code to
implement the -makedcls feature. The -reference feature
was contributed by Gerome Emmanuel, Ecole des mines, U.
Nancy (slightly modified). The patch for Cray pointer
syntax was provided by John Dannenhoffer of United Tech-
nologies Research Center. Additional features will be
added as time permits. With Version 2.5, the name was
changed from forchek to ftnchek, to avoid confusion with a
similar program named forcheck, developed earlier at Lei-
den University.
We would like to thank John Amor of the University of
British Columbia, Reg Clemens of the Air Force Phillips
Lab in Albuquerque, Markus Draxler of the University of
Stuttgart, Victor Eijkhout of the University of Tennessee
at Knoxville, Greg Flint of Purdue University, Daniel P.
Giesy of NASA Langley Research Center, Fritz Keinert of
Iowa State University, Judah Milgram of the University of
Maryland College Park, Hugh Nicholas of the Pittsburgh
Supercomputing Center, Dan Severance of Yale University,
Phil Sterne of Lawrence Livermore National Laboratory,
Larry Weissman of the University of Washington, Warren J.
Wiscombe of NASA Goddard, and especially Nelson H. F.
Beebe of the University of Utah, for pointing out bugs and
suggesting some improvements. We also thank Jack Dongarra
for putting ftnchek into the netlib library of publicly
available software.
INSTALLATION AND SUPPORT
The ftnchek program can be obtained by anonymous ftp from
many software servers, including host netlib.org
(128.169.92.17) where it is located in directory /fortran.
Installation requires a C compiler for your computer. See
the README file provided with the distribution for
instructions on installing ftnchek on your system. Exe-
cutable binary in ZIP format for IBM PC computers under
MS-DOS is available by anonymous ftp from oak.oakland.edu
(141.210.10.117) where it is located in directory /Sim-
Tel/msdos/fortran, filename ftnchk28.zip. Executable
binary in binhexed stuffit format for Macintosh computers
is available from sumex-aim.stanford.edu (36.44.0.6), in
directory info-mac/Development, filename ftnchek-28.hqx.
The nroff version of this document is named ftnchek.man.
On UNIX systems, it can be used as the man page or you can
print it using the command nroff -man ftnchek.man | lpr.
2 June 1995 54
FTNCHEK 2.8.3(1L) FTNCHEK 2.8.3(1L)
The distribution also includes a plain ASCII version named
ftnchek.doc, a PostScript version named ftnchek.ps, and a
VMS HELP version named ftnchek.hlp.
Information about the latest version and the status of the
project can be obtained by the Internet command ``finger
ftnchek@mary.fordham.edu''. For further information and
to report bugs, you may contact Dr. Robert Moniot at
either of the following network addresses:
MONIOT@FORDMULC.BITNET
moniot@mary.fordham.edu
SEE ALSO
dcl2inc(1L), dtoq(1L), dtos(1L), f77(1), fd2s(1L),
fs2d(1L), pfort(1L), qtod(1L), sf3(1L), stod(1L).
xsf3(1L).
2 June 1995 55